JP2009254180A - Power device for cutting and welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power device being capable of using one power device by a different current-voltage characteristic specification and having a simple structure having an output power transformer. <P>SOLUTION: A rectifier converting ACs into DCs, an inverter being connected to the rectifier, converting DCs into ACs and transmitting ACs to the secondary side of the output power transformer and a current sensor detecting a current value transmitted to the secondary side by the inverter are fitted on the primary side of the output power transformer. A control circuit comparing the current value detected by the current sensor with a reference value and supplying a power on the primary side while using a current supplied to the inverter as a DC constant current by a feedback control to the inverter when these current value and reference value mutually differ is further fitted to the primary side of the output power transformer. An intermediate terminal connected to the intermediate section of the output power transformer is mounted on the secondary side of the output power transformer, and an constant-current characteristic output having a desired dimension is extracted on the secondary side from the power as a constant current on the primary side through the intermediate terminal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply device, and more particularly to a cutting and welding power supply device including an output power transformer.

  For example, it has become desirable to be able to use a plasma cutting apparatus as disclosed in Japanese Patent No. 103883005 for coated arc welding.

  In general, in order to perform plasma cutting, the no-load voltage value is set high in order to facilitate the ignition (ignition) of an arc between a base material (cut object or nozzle) and an electrode (non-consumable electrode). There is a need. For these reasons, the current-voltage characteristics of the power supply device used in the plasma cutting device are required to be high voltage and low current. On the other hand, in order to perform covered arc welding, it is necessary to maintain an appropriate arc length even if the operator's hand fluctuates, so the electric characteristics of the power supply to be applied are constant current characteristics (droop characteristics) and the welding voltage It is necessary that the welding current does not change even if (arc length) changes. For these reasons, the current-voltage characteristics of the power supply device used for coated arc welding are required to be low voltage and large current, contrary to the case of plasma cutting. As described above, the power supply device used in the plasma cutting apparatus can be used in a coated arc welding apparatus, or can be used in a combined apparatus for a plasma cutting apparatus and a coated arc welding apparatus. It is necessary to achieve conflicting current-voltage characteristics in the power supply device.

  In particular, here, there is a problem that it is difficult to obtain a constant current characteristic (a drooping characteristic) necessary when performing the covering arc welding. Conventionally, a constant current characteristic is obtained by providing a current detection sensor (CT) on the secondary side of the output power transformer of the power supply device and using the current detected by the current detection sensor (CT) between the secondary side and the primary side. It was supposed to be achieved by performing feedback control. However, when this conventional configuration is applied to a power supply device used for both a plasma cutting device and a coated arc welding device, a large current used in a coated arc welding device by a current detection sensor (CT) provided on the secondary side. The current is suddenly detected, and as a result, it is expected that feedback control is substantially impossible. Other conventional means for obtaining constant current characteristics include the use of a power transformer using a magnetic leakage transformer in which the output voltage on the secondary side of the transformer drops in inverse proportion to the increase in load current. However, in this case as well, when a large current is used, it is difficult to obtain a constant current characteristic, and it is expected that only a drooping characteristic output is obtained.

Patent 103883005

  The present invention has been made to solve such problems in the prior art, and it is possible to use one power supply device with different current-voltage characteristics by performing feedback control only on the primary side. An object of the present invention is to provide a power supply device having a simple structure including an output power transformer.

  The power supply device according to the present invention is a power supply device provided with an output power transformer, and the primary side of the output power transformer is supplied with a constant current by providing a DC constant current characteristic, and the output On the secondary side of the power transformer, a constant current characteristic output current having a desired magnitude is extracted from the power supplied on the primary side via an intermediate terminal connected to the middle of the output power transformer.

  The power supply device according to the present invention is a power supply device including an output power transformer, and a rectifier that converts alternating current into direct current on the primary side of the output power transformer, and a direct current that is connected to the rectifier and converts into direct current An inverter that transmits to the secondary side of the output power transformer, a current detection sensor that detects a current value transmitted to the secondary side by the inverter, and a current value detected by the current detection sensor as a reference value When these are different from each other, there is provided a control circuit that performs feedback control on the inverter and supplies electric power as a constant current on the primary side as a DC constant current that is supplied to the inverter, An intermediate terminal connected to the middle of the output power transformer is provided on the secondary side of the output power transformer, and the primary terminal is provided via the intermediate terminal. Wherein the retrieving of the desired from the power the magnitude of the current in the secondary side.

  In the power supply apparatus, the inverter is formed of an insulated gate transistor, and the control circuit matches a current value detected by the current detection sensor with the reference value to set a constant current characteristic as a constant current characteristic setting value. A variable resistor for setting; a comparator that outputs a signal corresponding to a difference between the set value and a predetermined current value; and a gate of the insulated gate transistor after pulse width modulation of the output from the comparator And a pulse modulation device that controls the output current value of the insulated gate transistor.

  In the power supply apparatus, a rectifier that converts alternating current taken out via the intermediate terminal into direct current may be further provided on the secondary side of the output power transformer.

  Furthermore, the power supply apparatus may be provided with a switch that can be switched to the intermediate terminal.

  Further, the current taken out on the secondary side through the intermediate terminal using the switch is for welding, and the current taken out on the secondary side without using the intermediate terminal is used for plasma cutting. Each can be used, and can also be used in a dual-purpose apparatus having both a plasma cutting function and a covering arc welding function.

  Hereinafter, a power supply device 1 according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. The power supply device 1 can be used for any of a plasma cutting device having a plasma cutting function, a covering arc welding device having a covering arc welding function, or a combined device having both functions. .

  FIG. 1 schematically shows a circuit diagram of the power supply device 1. The power supply device 1 includes an output power transformer composed of a primary side and a secondary side. The primary side 3 is shown on the left side of FIG. 1, and the secondary side 5 is shown on the right side of FIG.

Primary 3 mainly includes a rectifier REC ₁ for converting an AC AC to DC DC, is connected to a rectifier REC _1, an inverter IN, and transmits the converted direct current to alternating current to the secondary side 5 of the output power transformer The current detection sensor CT detects a current value transmitted to the secondary side 5 by the inverter IN, and further includes a control circuit 7 that performs control according to the value of the current detected by the current detection sensor CT. Here, it should be noted that the current detection sensor CT is provided not on the secondary side but on the primary side. By adopting such a configuration, it is possible to prevent the feedback control on the primary side from being affected by the (large) current on the secondary side, and to always provide a stable constant current characteristic on the primary side. . In addition, by using the constant current on the primary side, it is possible to always provide stable current-voltage characteristics on the secondary side.

When the direct current generated by the rectifier REC ₁ is transmitted to the secondary side 5, the direct current is converted into alternating current using the insulated gate transistors IGBT ₁ and IGBT ₂ constituting the inverter IN. The current detection sensor CT is connected between the insulated gate transistors IGBT ₁ and IGBT ₂ and the secondary side 5 and detects a current value transmitted to the secondary side 5 by the inverter IN. The sensed current can then be utilized by the control circuit 7 for feedback control.

The control circuit 7 mainly includes a constant current reference setting variable resistor RV that matches a current value detected by the current detection sensor with a reference value set by using the resistor R ₃ and sets the constant current characteristic as a set value. A comparator C for outputting a signal corresponding to a difference between a predetermined current value determined in advance using the resistors R ₁ and R ₂ and a set value in the variable resistor RV for constant current reference setting; and the comparator C Are connected in parallel to each other, and a comparator adjusting variable resistor G for adjusting the comparison sensitivity in the comparator C is further applied to the gates of the insulated gate transistors IGBT ₁ and IGBT ₂ after pulse width modulation of the output from the comparator C. The pulse modulation device PWM is provided to control the output current value of the insulated gate transistor IGBT.

  On the primary side 3, using the above configuration, when it is found that the current value detected by the current detection sensor CT is different from the reference value, feedback control is performed to the inverter IN through the current detection sensor CT and the control circuit 7. I do. With this feedback control, the current supplied to the inverter IN is a constant DC constant current or a DC constant current within a predetermined range, and the power on the primary side 3 is independent of the load fluctuation on the secondary side 5. It is almost constant.

With respect to the primary side 3, the secondary side 5 is mainly taken out from the primary side 3 via the intermediate terminal MT connected to the middle of the output power transformer of the secondary side 5 and the intermediate terminal MT. A rectifier REC ₂ for converting the alternating current into direct current, a switch SW that is switchably connected to the intermediate terminal MT for taking out the alternating current through the intermediate terminal MT, and further connected to one (b) of the connectors a and b. Of the supersaturated reactor L. Here, different members are connected to the connectors a and b depending on whether the power supply device 1 is used for a plasma cutting device or a coated arc welding device.

For example, when the power supply device 1 is used for a plasma cutting device, a plasma switching torch is connected to the connectors a and b and an arc is generated between them as shown in FIG. . In this case, for example, plasma cutting can be performed with an output of constant current characteristics of 235 (V) and 8 (A). On the other hand, when the power supply apparatus 1 is used for a coated arc welding apparatus, as shown in FIG. 2 b), a welding holder is connected to the connectors a and b. The welding rod 9 is connected to an object such as an iron plate to be welded to the other connector b, and, for example, covering arc welding is performed with outputs of constant current characteristics of 42 (V) and 45 (A). be able to. The supersaturated reactor L connected between the connector b and the rectifier REC ₂ smoothes the output ripple waveform at the connector b, and in particular, stabilizes the arc generated when used for a coated arc welding apparatus. Has the function of

  In order to use the power supply device 1 for both the plasma cutting device and the coated arc welding device, it is necessary to switch between the plasma cutting device and the coated arc welding device. This switching can be easily performed using a switch SW provided on the secondary side 5. For example, when the switch SW is in the P position shown in FIG. 1, the current is extracted without using the intermediate terminal MT, and the extracted current is used for the plasma cutting device. On the other hand, when the switch SW is switched from the P position to the W position, since the current is taken out through the intermediate terminal MT, the voltage is controlled and the constant current on the primary side 3 is set according to the magnitude of the voltage. A desired amount of current can be extracted from the power at the secondary side 5. The current thus taken is used for the coated arc welding apparatus.

  Next, the operating principle of the power supply device 1 will be described with reference to FIG. In FIG. 3, the horizontal axis indicates the current value, the vertical axis indicates the voltage value, and “A” indicates the characteristic relationship between the current and voltage when the power supply device 1 is used for a plasma cutting device, and “A”. These respectively show the characteristic relationship of an electric current (horizontal axis) and a voltage (vertical axis) when the power supply device 1 is used for a covering arc welding apparatus.

  As is apparent, the power when the power supply device 1 is used for the plasma cutting device, that is, the cutting power (Pc), can be expressed as cutting voltage (Vc) × cutting current (Ac), The electric power when the power supply device 1 is used in the coated arc welding apparatus, that is, the welding power (Pw) can be expressed by welding voltage (Vw) × welding voltage (Vw). When the same power supply device 1 is used for both the plasma cutting device and the coated arc welding device, the maximum power when used for the plasma cutting device and when used for the coated arc welding device. The maximum power must be equal, that is, satisfy the relationship of cutting power (Pc) = welding power (Pw), in other words, the area of “A” and the area of “A” shown in FIG. It becomes. Further, when the power supply device 1 is used for a plasma cutting device, the cutting voltage (Vc) must be set to a high voltage value of about 235 V, for example, in order to maintain the plasma arc length. When used for welding equipment, the welding current (Aw) must be a high current value, for example about 45A, in order to ensure the amount of weld metal, in addition to the need for maximum power, It is necessary to satisfy the request.

  In order to satisfy these needs, in the power supply device 1, the primary side of the output power transformer is provided with a DC constant current characteristic (or DC droop characteristic) so that the power is always constant. When the intermediate terminal MT and the switch SW are provided on the secondary side and the power supply device 1 is used for a plasma cutting device, the switch SW is set to the P position and the current on the secondary side is, for example, about 8 A or more at the maximum. When the power supply device 1 is used for a coated arc welding apparatus, the switch SW can be switched to the W position. Thus, the voltage on the secondary side is set to about 42V, for example, and the current can be suppressed to about 45A. As is apparent, the power values on the primary side and the secondary side of the transformer are always constant, for example, about 1880 W (8 A × 235 V, 45 A × 42 V) regardless of plasma cutting and covering arc welding.

Finally, Table 1 shows an example of the conditions for plasma cutting and covering arc welding that can be performed using the power supply device 1.

  The power supply device of the present invention is particularly suitable for use in a combined device of a plasma cutting device and a coated arc welding device, but is not limited to such a combined device and requires different types of current-voltage characteristics. It can be used for various devices. Moreover, although the example which provides only one intermediate terminal was shown in the above embodiment, of course, a plurality of intermediate terminals may be provided. In this case, the intermediate terminal is connected to various intermediate positions on the secondary side of the output power transformer in order to obtain a plurality of current-voltage characteristics. Furthermore, although this embodiment was demonstrated as what uses a covering arc welding, ie, a welding rod, this invention is applicable also to the plasma welding which does not use this.

It is a figure showing roughly the circuit diagram of the power unit by one embodiment of the present invention. It is the figure which showed notionally the different usage condition of the power supply device by one Embodiment of this invention. It is a figure explaining the principle of operation of the power unit by one embodiment of the present invention.

Explanation of symbols

1 Power supply 3 Primary side 5 Secondary side

Claims (6)

A power supply device having an output power transformer,
The primary side of the output power transformer is supplied with constant current power by providing a DC constant current characteristic,
On the secondary side of the output power transformer, a constant current characteristic output current of a desired magnitude is extracted from the supply power on the primary side via an intermediate terminal connected to the middle of the output power transformer. Power supply. A power supply device having an output power transformer,
On the primary side of the output power transformer,
A rectifier that converts alternating current to direct current; an inverter that is connected to the rectifier, converts direct current to alternating current and transmits it to the secondary side of the output power transformer; and a current value transmitted to the secondary side by the inverter. The current detection sensor to be detected and the current value detected by the current detection sensor are matched with a reference value, and when these are different from each other, feedback control is performed on the inverter and the current supplied to the inverter is set as a DC constant current. A control circuit for supplying power as a constant current on the primary side is provided;
On the secondary side of the output power transformer,
An intermediate terminal connected to the middle of the output power transformer is provided, and a constant current characteristic output current having a desired magnitude is taken out from the supplied power on the primary side via the intermediate terminal on the secondary side. A power supply characterized by.   The inverter includes an insulated gate transistor, and the control circuit matches a current value detected by the current detection sensor with the reference value to set a constant current characteristic setting variable resistor. A comparator that outputs a signal corresponding to a difference between the set value and a predetermined current value, and an output from the comparator is applied to the gate of the insulated gate transistor after pulse width modulation is performed. The power supply device according to claim 2, further comprising: a pulse modulation device that controls an output current value of the insulated gate transistor.   4. The power supply device according to claim 1, further comprising a rectifier that converts alternating current taken out via the intermediate terminal into direct current on a secondary side of the output power transformer. 5.   The power supply device according to claim 1, further comprising a switch that can be connected to the intermediate terminal in a switchable manner.   The current taken out on the secondary side through the intermediate terminal using the switch is for welding, and the current taken out on the secondary side without using the intermediate terminal is used for plasma cutting, respectively. 6. The power supply device according to claim 5, which can be used in a dual-purpose device having both a plasma cutting function and a covering arc welding function.

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